Apparatus for controlling power consumption in lighting loads and the like

ABSTRACT

Apparatus for interrupting power to a plurality of parallel loads such as lighting circuits and selectively reapplying power to the loads includes a first switch serially interconnecting the loads to a power line. Second switch circuits are serially connected with each load whereby interruption of power to a load for a predetermined period of time opens the switch circuits. The switch circuits include bidirectional conduction devices such as triacs which require a gating signal before becoming conductive. A resistor-capacitor circuit provides a gating signal to the triac to maintain conduction thereof for the predetermined period of time.

This invention relates generally to apparatus for controlling electricalpower consumption of voltage regulatable loads such as lighting loads inoffice buildings, industrial plants, schools, and other like facilities.More particularly, the invention relates to apparatus which can controlpower consumption in a plurality of loads and which allows selectiveenergization of the loads.

Energy conservation is a major concern today. One effective method ofconserving energy is through regulation of power consumption wherebyunnecessary power usage is eliminated. Disclosed in U.S. Pat. No.4,189,664 and No. 4,219,759 are power control units for automaticallyregulating power consumption in single phase and three phase loads suchas lighting circuitry in accordance with load demands. For example,during daylight hours and also during cleaning at night the requisitelight level drops and power consumption can be reduced by lowering thelevel of the voltage applied to the load. At other times when full lightoutput is required the voltage levels are increased accordingly.

In large facilities having many lighting circuits a need exists formeans for extinguishing current in all of the lighting circuits butwhich allows selective re-energization of the lighting circuits. Forexample, in a large office building which is essentially vacated afternormal business hours, switch means can be provided for automaticallyturning off all lights. However, should any one area of the buildingrequire light output, an override switch should be provided in that areato allow the selective energization of the required lighting circuit.

Accordingly, an object of the present invention is apparatus forautomatically removing power from a plurality of loads with means forthereafter allowing power application to selective loads.

Another object of the invention is control circuitry for a load whichautomatically interrupts a load circuit in response to a momentaryremoval of supply voltage and which can be selectively reset forconduction of load current.

Still another object of the invention is apparatus for automaticallyextinguishing current in a plurality of lighting circuits and in whichselective circuits can thereafter be locally re-energized.

A feature of the invention is switch means for providing an air gap offposition, an on position, and a reset position.

Another feature of the invention is means for indicating power at an onswitch which must be reset.

Briefly, apparatus for controlling energization of a plurality ofparallel loads and allowing selective re-energization of the pluralityof loads in accordance with the invention comprises first switch meansserially connected with the plurality of parallel loads for removing andapplying power to all of the loads. Second switch means is associatedwith each of the loads with each switch means including a first switchhaving a first position for removing power to its associated load and asecond position for applying power. A second switch is seriallyconnected with the first switch and the load, and control means isprovided for the second switch whereby the second switch is opened inresponse to opening of the first switch or the loss of power for apredetermined period of time, and is closed in response to closing of areset switch.

In a preferred embodiment the second switch comprises a triac having ananode terminal, a cathode terminal, and a gate terminal. Control meansresponsive to the reset switch applies a conductive signal to the gateterminal of the triac. Advantageously, the reset switch can include athird position of the first switch with conductive means seriallyconnecting the third position of the first switch to the gate electrodeof the triac.

In accordance with one feature of the invention the control means mayinclude timing means for maintaining the conductance of the secondswitch and opening the second switch after a predetermined time intervalafter removal of power to a load.

The invention and objects and features thereof will be more readilyapparent from the following detailed description and appended claimswhen taken with the drawing, in which:

FIGS. 1A-1D are schematics illustrating the operation of apparatus inaccordance with the invention.

FIG. 2 is a detailed schematic of one embodiment of the presentinvention.

FIG. 3 is a detailed schematic of another embodiment in accordance withthe invention.

Referring now to the drawings, FIGS. 1A-1D are functional block diagramsillustrating operation of apparatus in accordance with the presentinvention. A plurality of loads 10, 12, and 14 such as lighting circuitsin a building are connected in parallel and through a switch means 16 toa power bus. The switch means 16 may comprise a switch in the masterpanel or power control units such as disclosed in U.S. Pat. Nos.4,129,759 and 4,189,664, supra. The provision of the switch 16 seriallyconnecting all of the loads to the power bus allows for the reduction ofpower or removal of power from all of the loads in response to energycurtailment or when power to the loads may no longer be required. Forexample, the switch 16 can be automatically controlled to remove powerfrom all of the lighting circuits of the building at a specified hour inthe evening, and to restore power to the loads at another specified timein the morning.

However, lighting may be required in certain parts of the building whenthe switch 16 has removed power, and provision of only the switch 16would be impractical.

In accordance with the invention second switch means 20, 22 and 24 areserially connected with the loads 10, 12 and 14, respectively to permitthe selective re-energization of the loads. Each of the switch means 20,22, 24 includes a single pole, single gang toggle switch which may havea configuration for positioning in a standard single gang handy box orknockout box that normally houses a conventional lighting switch. Eachof the toggle switches includes a manually positionable lever 21, 23,and 25 which, as will be described in more detail hereinbelow, can bemoved to one of three switch positions: On, Off, and Reset.

In FIG. 1A, switch 16 is closed in normal operation and switches 20 and22 are closed with loads 10 and 12 energized. Switch 24 is in an openposition and load 14 is not energized. As will be described furtherhereinbelow the lever 25 is provided with a light indicating that poweris available for load 14. In FIG. 1B switch 16 is opened and power isremoved from the loads 10 and 12. After switch 16 has been opened for apredetermined period of time, the switch is again closed as in FIG. 1Cbut power is not applied to the loads 10 and 12. Light indicatorsincorporated in the manual levers 21 and 23 indicate that power isavailable at the switches.

Assuming that it is desired to re-energize the lighting load 12, lever23 of switch means 22 is moved to a third reset position and controlmeans reactivates the switch means for applying power to load 12, asindicated. Thus, the opening of the master switch 16 removes power fromall of the loads, and power can be reapplied selectively to each of theloads by resetting the switch means serially connected with the loads.

Referring now to FIG. 2, a detailed schematic of one embodiment of theapparatus (such as switches 20, 22, 24 of FIG. 1) for selectivelyre-energizing a load is illustrated. The load circuit includes a firstswitch 30 and a second switch 32 serially connected with a load 34between the A.C. power input lines. As above described, the switch 30preferably comprises a single pole, three position switch having an onposition, an off (air-gap) position, and a reset position, as will bedescribed hereinbelow. Advantageously, a light indicator such as a lamp36 can be positioned in the lever of switch 30 and serially connectedthrough a resistor 38 across the input lines to indicate the presence ofpower at the switch. Switch 32 is a bidirectional conductive device suchas a triac having an anode terminal, a cathode terminal and a controlterminal.

With electrical power present, switch 30 closed, and triac 32conducting, current will flow through the load 34. However, the removalof power or the opening of switch 30 interrupts the flow of currentthrough load 34, and after a predetermined period of time the conductionof triac 32 is extinguished. Thereafter, upon the reapplication of powerand the closing of switch 30 load current remains extinguished until thetriac 32 receives a conduction signal at the gate electrode.

Control circuitry shown generally at 40 is provided to apply aconduction signal to triac 32. Preferably, switch 30 has a third resetposition where the switch remains closed and also closes a switch 42 inthe control circuitry. The control circuitry comprises a bridgecomprising diodes 44, 45, 46, and 47 which are connected across thepower lines through resistors 48 and 49. A silicon controlled rectifier(SCR) 50 is serially connected with resistor 52 between the cathodes ofdiodes 44, 45 and the anodes of diodes 46, 47 whereby a positive voltagedifferential can be applied across the anode and cathode of SCR 50during alternate half-cycles of the input line voltage.

When switch 42 is momentarily closed a positive trigger voltage isapplied to the control electrode of the SCR 50 through resistor 54. TheSCR is rendered conductive and a current flows through the SCR 50 andresistor 52 thereby charging a capacitor 56 connected across resistor 52through diode 60. Zenner diode 58 and capacitor 59 are also connected inparallel with resistor 52 to limit the voltage thereacross. The chargeon capacitor 56 is applied through resistor 54 to maintain the SCR 50conductive.

Current passing through the SCR 50 is communicated through diode 47 tothe gate electrode of triac 32 thereby rendering triac 32 conductive.Thereafter, triac 32 will remain conductive so long as load currentpasses therethrough.

Upon removal of power to switch 30, current ceases to flow through SCR50. However, a conductive signal is maintained on the control electrodeof SCR 50 by the charge on capacitor 56 for a time period determined bythe time constant of capacitor 56 and resistor 52. Thus, reapplicationof power to switch 30 during this time interval will permit current toflow through the SCR 50 and again apply a trigger voltage to triac 32.However, after the time interval established by resistor 52 andcapacitor 56, the SCR 50 becomes non-conductive and the reapplication ofpower through switch 30 will not produce a current through SCR 50. Thus,a conductive signal is not reapplied to triac 32 after the predeterminedtime interval.

To again fire the SCR 50 the reset switch 42 which is ganged to switch30 must again be closed by moving switch 30 to a reset position andthereby reapplying a trigger voltage through resistor 54 to the controlterminal of SCR 50. Accordingly, the conduction of triac 32 is dependenton the availability of power at switch 30 and a conduction signal fromthe control means.

Referring now to FIG. 3, another embodiment of circuitry in accordancewith the invention is illustrated. In this embodiment the A.C. linevoltage is applied through on/off switch 60 and a power triac 62 to theload 64. A capacitor 66 is provided for filtering purposes. The timingcircuit in this embodiment comprises a capacitor 68 and a resistor 70which shunts capacitor 68 through the diode 72. Capacitor 68 provides atrigger voltage to the triac 62 through serially connected diodes 72 and74. A second, low voltage triac 76 provides a charging circuit forcapaitor 68 through diode 72 and resistor 75. Resistor 78 interconnectscapacitor 68 and the gate electrode of triac 76.

In operation, to initially render the apparatus conductive whencapacitor 68 is discharged, the three position switch 60 momentarilycloses reset switch 80 which applies a gating voltage to triac 62through resistor 75 and diode 74. Thereafter, assuming that line voltageis maintained, triac 62 remains conductive and applies current to theload 64. Initial current through capacitor 68 applies a trigger signalto triac 76 through resistor 78, and the conduction of triac 76 providesa charging circuit for capacitor 68 during the negative half cycles ofthe line input voltage. Consequently, in the event of momentary loss ofinput line voltage capacitor 68 maintains sufficient voltage on the gateof triac 62 to maintain the conductive state thereof for a time perioddetermined by the time constant of capacitor 68 and resistor 70 alongwith the impedances of diodes 72 and 74 and triac 62. However, when theline voltage is interrupted for a sufficient length of time for thecapacitor 68 to discharge below the firing voltage level of triac 62,the circuit reverts to a nonconductive state, and the reset switch 80must again be closed before the circuit becomes conductive.

Switch apparatus in accordance with the present invention has proved tobe useful in lighting applications by permitting the automaticextinction of currents in a plurality of loads while permittingselective light circuits to be re-energized. The apparatus is readilymounted in a conventional lighting switch box and is simple to install.While the invention has been described with reference to specificembodiments, the description is illustrative of the invention and is notto be construed as limiting the invention. Various modifications andapplications may occur to those skilled in the art without departingfrom the true spirit and scope of the invention as defined by theappended claims.

What is claimed is:
 1. A method of controlling power consumption in aplurality of lighting circuits connected in parallel and maintainingconduction of said load circuits after a momentary loss of electricalpower comprising the steps of:providing a first switch means in serieswith all loads for removing electrical power to all loads on opening ofsaid first switch means, providing a plurality of second switch means,each of said second switch means being serially connected with a load,each of said second switch means including first and second seriallyconnected switches each having a conducting state and a non-conductingstate, said first switch having an off position for immediately removingpower to a load, an on position, and a reset position and said secondswitch having a conduction gating terminal and control means forapplying an ignition signal to said conduction gating terminal and formaintaining ignition signal for a limited period of time after removalof power and thereafter rendering said second switch non-conductive,said control means reapplying the ignition signal upon movement of saidfirst switch to said reset position and thereby reigniting said secondswitch removing electrical power to all loads by opening said firstswitch means for at least said limited period of time, reclosing saidfirst switch means, and selectively reenergizing a lighting circuit bymoving a first switch to said reset position thereby applying anignition signal to the conduction gating terminal of the seriallyconnected second switch.